Process for the manufacture of arsenic acid



Cit

Patented den, 22, lzfi. i

IFHITZ ULLMANN, 03E GQI'TENBURG,

MD GEEK TREWIENDT, OF BERLIN, GER- MANLsMEKGHQBEl T0 ll. MICHAEL do 30., 0F BERLIN, GERMANY.

PHOGEElfi FUR THE MANUFJZLUTURE 01h" ARSENIG ACID.

l lo Drawing; Application filed February 26, 1924,

T l 's invention relates to the manufacture of arsenic acid from arsenic trioxide and/or arsenic by means of an acid catalytic of extremely low cost.

Arsenic acid has heretofore been made by an oxidation process with nitric acid.

Arsenic acid has also heretofore been made from a mixture of arsenic, chloratcot' sodium and 'ater, a solution of tetraoxide of osmium being added as a catalyzer.

The nitric acid process requires extensive and costly plant installation because of the necessity for regeneration of the nascent nitric gases, and has the disadvantage that this process involves lossot nitrogen as Well as loss of arsenicthroug'h the formation of insoluble arsenical slush residues.

The catalytic method by the use of tetraoride of osmium has not the disadvantages of the nitric acid-process but because of the extremely high cost of the catalyzing agent, has not and probably never-Will come into extensive commercial use.

The object of our invention is to use the catalytic method but with a catalytic'agent of such low cost as to permit of the production of arsenic acid by such method coinmercially, in which there remains no residue, no loss of arsenical material, and no poisonous fumes produced during oxidation.

13y experiment and research, We have discovered that certain acids may be used as catalytics in the production of arsenic acid, among. them being hydrochloric acid and vanadic acid, and thus all the advantages of the catalytic method are obtained at a cost considerably less than the nitric acid method, without the large expenditure for plant and equipment which the latter process requires, and with the ability to employ a catalytic much below the cost or the expensive catalytic tctraoxide of osmium.

A process comprising the use of hydro chloric acid is claimed in applicants co-pendin application now Patent No. 1,677,257, of July 17, 1928.

There are a variety or ways in which our invention can be used, and within reasonable limits the quantities of the chemicals used may he period and some i' hstitutions may he made, as, for instance. the suhstitution of arsenic (Aslfor trio); e of arsenic (As,0,), iviihout departing from the principle involved in our process.

Serial No. 395,340, and in Germany March. 6, 19%.

"'tinctly understood that this example is for the purpose of illustration only and is not to be treated a limitation of our invention. Said example is as follows: 1

A mixture 0t 10 parts oftrioaide of or sonic A3 0,), 20 partsot water (HES), and {3.8 parts of chlorate of sodium (hlaClU,) is heated to boiling temperature and then 0.? parts of hydrochloric acid (HGl) in a solution of 1.1 specific gravity is slowly added tothe mixture. With the violent reaction the trioxide of arsenic will soon dissolve and a solution of arsenic acid is obtained.

The solution of arsenic acid obtained lay this process is particularly adapted for use in the production of arsenate of calcium, an msectieide of particular value in controlling the boll Weevil and other crop parasites.

We Wish it distinctly understood that our invention can be practiced by changing the chemical formula above indicated, by using other chlorates, as, for instance, a chlorate of potassium (KCHL) in place of chlorate of sodium lii'aClO but that such change is only for the purpose of further illustration and not as defining the limits or scope of our invention. a

iVe also Wish it distinctly understood that in the example given, somewhat equivalent results will be obtained if. substantially the samenumber of parts are taken of the equivalent substance, that is, 10 parts of a substance containing a form of arsenic in the lower state of oxidation; 3.8 parts of the equivalent chlorate above noted; 0.? parts of u non-nitrogenous acid having a specific gravity o l 1.1.

In theX-luhns though I claim acids as my preferred catalytic agen s, I consider for certain purposes vanadic salts, copper salts or the like as equivalents.

lid

liming; flesmri'bad 0m: inventidn What we chum and Lemma 5513mm by Lettars Pm"- Qm. 1a:

1. The I pmcess of making amenic acid which censists in heating (:0 bailing a, solution comprising lflpais 0f arsenic trioxide, 2G parts of waterand 38 parts of potassium chlorate, and 9mm miciing'therete a small amount vi acid,

The pmwass which consists in heating to beiling a s01ution comprising apprwimmiely twice as much Water as arsenic of :1- lwwer valwce and apo-f nmking arsenic acid proximately une-fifih as much of wtassium "chlorate as water, and then. adding thereto 15 a small amnunt of acid.

3. The process of making arsenic acid which consists in heating to boiling a solution comprising a'pproxiumtely 10 parts of arsenic trioxide and 4 parts 0 an oxidizing 20 agent, and adding thereto a small amnunt of acid. This specification signed this 15511 day of January, 1924.

- FRITZ UIJLMANN.

GERT 'IRIIWEN'DT. 

